Protein kinases are a class of important enzymes that catalyze the transfer of a phosphate group from ATP to serine, threonine, tyrosine, and histidine residues of peptides and proteins. The specificity of kinases is controlled by kinase recognition motifs, which are amino acid residues surrounding the amino acid to be phosphorylated. This phosphorylation reaction is ubiquitous in life and is an essential step in many intracellular signal transduction pathways. The importance of protein phosphorylation as a regulatory process means that kinase inhibitors are potentially highly valuable therapeutic agents for many diseases.
Sensitive and broadly applicable methods for real time measurement of kinase activity are acutely needed by the biosciences research community, from basic investigation of enzyme mechanisms to systems biology to drug discovery. Traditional assays utilize radioactive material (e.g., 32P), which can be expensive, dangerous and can pose problems for disposal. Other methods for studying kinases include fluorescence. In general, current fluorometric methods, while safer than radioactivity, may not be bright enough to discern signal-to-noise ratio. In addition, background fluorescence in the assay environment may also interfere with accurate fluorescent measurement.
U.S. Pat. No. 6,906,194, describes sulfonamide substituted quinoline compounds having the structure:

for use in kinase detection. Although safe and sensitive, the sulfonamide substituted quinoline compounds are not very bright.
What is needed is a safe kinase assay that can provide accurate, reliable signal for the measurement of kinase activity, with increased brightness and sensitivity. For example, fluorescent kinase assays where the ideal fluorophores used would be bright enough to provide adequate signal to noise, and are red-shifted away from commonly occurring background fluorescence found in cell lysates, live cells, and drug candidate compounds and libraries.